Approximately 75% of pregnant women experience gum bleeding due to the hormonal changes during pregnancy.

These findings – by Yiping Han, a researcher from Department of Periodontics at Case Western Reserve University School of Dental Medicine – are discussed in an article in the February issue of Obstetrics & Gynecology.

The article explains that bleeding in the gums allows bacteria in the mouth to enter the bloodstream and potentially infect a foetus – but can be stopped by the immune system.

However, in this case, the mother also experienced an upper respiratory infection like a cold and low-grade fever just a few days before the stillbirth.

Lead author, Yiping Han, said: ‘There is an old wives' tale that you lose a tooth for each baby, and this is due to the underlying changes during pregnancy.

‘But if there is another underlying condition in the background, then you may lose more than a tooth.'

Even though the amniotic fluid was not available for testing, Han suspects from work with animal models that the bacteria entered the immune-free amniotic fluid and eventually ingested by the baby.

‘The timing is important here because it fits the timeframe of haematogenous (through the blood) spreading we observed in animals,' Han said.

Post-mortem microbial studies of the baby found the presence of F. nucleatum in the lungs and stomach. The baby had died from a septic infection and inflammation caused by bacteria.

After questioning the mother about her health during the pregnancy, Han arranged for her to visit a periodontist, who collected plaque samples from her teeth.

Using DNA cloning technologies, Han found a match in the bacterium in the mother's mouth with the bacterium in the baby's infected lungs and stomach.

'The testing strongly suggested the bacteria were delivered through the blood,' Han said.

With preventive periodontal treatment and oral health care, the mother has since given birth to a healthy baby.

Han says this points again to the growing importance of good oral health care.